3D-Printed Screw-In Front Lenscaps With Optional QR Code

My thing http://www.thingiverse.com/thing:414556 was a really quick and easy 3D-printable screw-in front lenscap design, set-up as a customizer application. __Less than $0.15 worth of materials__ are used to make a typical size lenscap, yet they work well and can even __double as color references__. An Instructable gives the details: http://www.instructables.com/id/3D-Printed-Screw-In-Front-Lenscaps/ .

__This thing is improved in three ways__ (demonstrated with the _green_ cap):
1. This us